1. Field of the Invention
The present invention relates to an automatic picture quality compensating method and apparatus adopting a fuzzy theory, and more particularly, to an automatic picture quality compensating system which generally analyzes a luminance signal level, horizontal high frequency components and vertical correlativity of the brightness signal, and an envelope of a picture image signal using fuzzy theory to optimally correct a profile of the picture image, thereby improving the picture image in quality.
2. Description of the Prior Art
Generally, in a video system such as a video cassette recorder, a color television or the like, a method in which the luminance signal is separated from a composite video signal to adjust the brightness of a picture screen has been proposed to improve the quality of the picture image.
Also, a method in which a high frequency signal having an amplitude below a constant level is extracted from an original video signal and the extracted high frequency signal is then subtracted from the original signal to control the picture image quality has been proposed as well.
For the method in which the luminance signal is extracted, only the brightness of the picture screen may be determined, on the other hand, with the method in which the high frequency component is extracted, even though the horizontal signal component of the picture image is improved, the vertical signal component of the image is likely to be deteriorated in quality or the signal-to-noise (S/N) ratio may be decreased.
Another examplary technique compensates for a preshoot or overshoot by using of a profile correcting circuit to produce a profile correcting signal and takes a signal of minimized deterioration of a signal-to-noise (S/N) ratio produced using a shoot waveform removing circuit on the basis of the profile correcting signal. The technique is disclosed in Japanese patent laid-open publication No. sho 63-14577. With the technique described in the Japanese publication, however, only the S/N ratio is increased. The brightness and high frequency component are not improved. Therefore, in the prior art the picture image cannot be improved in quality satisfactorily.